Field of the Invention
The present invention relates to data storage devices with flash memory and flash memory control methods.
Description of the Related Art
Flash memory, e.g., NAND flash, is commonly used as the data storage medium of today's data storage devices.
For example, flash memory is typically used in memory cards, USB flash devices, solid-state drives, and so on. In another application with multi-chip package technology, a NAND flash chip and a controller chip are combined in one package as an embedded multimedia card (e.g. an eMMC).
The physical storage space of a flash memory is divided into blocks, and each block includes a plurality of pages. An erase operation designed to reuse the storage space of the flash memory is performed on a block-by-block basis, to release space one block at a time. When updating data, the new data is written into a spare space and the space storing the old data is labeled “invalid.” In comparison with other types of data storage mediums, it is more complex to manage a flash memory. A specially designed controller for flash memory, therefore, is required.
The shrinking size of semiconductor devices may threaten the reliability of a flash memory. Especially, cosmic particle impacts (e.g. neutron strikes) may cause a certain degree of damage to the highly sophisticated semiconductor device. The data in the storage space hit by cosmic particles may be damaged.